Isotopident

Isotopident is a tool that helps you to estimate the theoretical isotopic
distribution of a peptide or protein, a polynucleotide and a chemical
compound from its composition (sequence of amino acids expressed in
either 1-letter code, sequence of amino acids expressed in 3-letter code,
sequence of nucleotides or its chemical formula). Moreover, Isotopident
is capable of computing its monoisotopic mass. Finally, this tool is also
able to predict the most likely isotope combination
and the exact mass of the given input. Please read the
documentation about this tool
(permitted input syntax, for example).